THURSDAY, July 27, 2017 (HealthDay News) -- Imagine if your muscles kept telling your brain you were exhausted, even when you were resting.

That's what it's like for those who struggle with chronic fatigue syndrome, and researchers suggest in a new report that they now know why.

The disorder may cause the body to amplify fatigue signals associated with physical activity, the researchers explained, which is why some patients become worn out just walking across a room.

"People with chronic fatigue are essentially sensing muscle metabolites [products produced when energy is expended] while they are not doing anything, and they're not supposed to be," said study author Dr. Roland Staud, a professor of rheumatology and clinical immunology at the University of Florida College of Medicine. "Generally speaking, when we're at rest, we don't feel our muscles."

The study involved 58 people with chronic fatigue syndrome, which is also known as systemic exertion intolerance disease (SEID). The researchers injected the participants' back and buttock muscles with either a solution of the painkiller lidocaine or a saline solution.

Staud's team found the lidocaine solution helped ease the patients' symptoms of exhaustion. The people who got these injections reported a 38 percent drop in their fatigue levels.

The researchers noted the findings suggest that the muscles and other peripheral tissues are involved in chronic fatigue. They concluded that lidocaine injections helped block the abnormal signaling of muscle metabolites.

More investigation is needed, but the study authors said their findings may lead to new treatment options for the 2.5 million Americans diagnosed with chronic fatigue syndrome, as well as people with other conditions associated with extreme exhaustion, such as lupus, cancer and depression.

"It's unlikely the central nervous system creates fatigue out of nothing," Staud said in a university news release. "It uses just very minute fatigue signals that it receives and inappropriately amplifies them, which results in significant impact on the quality of life of these individuals."